our complex origins

Ancient Arabian Stones Hint at How Humans Migrated Out of Africa            

Previous research had suggested that the exodus from Africa started between 70,000 and 40,000 years ago. However, a genetic analysis reported in April hinted that modern humans might have begun their march across the globe as early as 130,000 years ago, and continued their expansion out of Africa in multiple waves.
In addition, stone artifacts recently unearthed in the Arabian Desert date to at least 100,000 years ago. This could be evidence of an early modern-human exodus out of Africa, scientists say. However, it’s possible that these artifacts weren’t created by modern humans; a number of now-extinct human lineages existed outside Africa before or at the same time when modern humans migrated there. For instance, the Neanderthals, the closest known extinct relatives of modern humans, lived in both Europe and Asia around that time.

To help shed light on the role the Arabian Peninsula might have played in the history of modern humans, scientists compared stone artifacts recently excavated from three sites in the Jubbah lake basin in northern Saudi Arabia with items from northeast Africa excavated in the 1960s. Both sets of artifacts were 70,000 to 125,000 years old. Back then, the areas that are now the Arabian and Sahara deserts were far more hospitable places to live than they are now, which could have made it easier for modern humans and related lineages to migrate out of Africa.

“Far from being a desert, the Arabian Peninsula between 130,000 and 75,000 years ago was a patchwork of grasslands and savanna environments, featuring extensive river networks running through the interior,” Scerri said.

The northeast African stone tools the researchers analyzed were similar to ones previously found near modern-human skeletons. The scientists found that stone artifacts at two of the three Arabian sites were “extremely similar” to the northeast African stone tools, Scerri told Live Science. At the very least, Scerri said, this finding suggests that there was some level of interaction between the groups in Africa and those in the Arabian Peninsula, and might hint that these Arabian tools were made by modern humans.

Surprisingly, Scerri said, tools from the third Arabian site the researchers analyzed were “completely different.” “This shows that there was a number of different tool-making traditions in northern Arabia during this time, often in very close proximity to each other,” she said.

One possible explanation for these differences is that the artifacts were made by different human lineages. Future research needs to uncover skeletal remains with ancient tools unearthed from the Arabian Peninsula to help solve this mystery, Scerri noted. Unless skeletal remains are found near such artifacts, it will remain uncertain whether modern humans or a different  human lineage might have made them.

“It seems likely that there were multiple dispersals into the Arabian Peninsula from Africa, some possibly very early in the history of Homo sapiens,” Scerri said. “It also seems likely that there may have been multiple dispersals into this region from other parts of Eurasia. These features are what make the Arabian Peninsula so interesting.”

Ancient migrants out of Africa and from Eurasia might have encountered a number of different populations in the Arabian Peninsula, Scerri said. Some of these groups may have adapted to their environment more than others had, which raises the intriguing question:

“Did the exchange of genes and knowledge between such groups contribute to our ultimate success as a species?” Scerri said.

Ancient Arabian Stones Hint at How Humans Migrated Out of Africa            

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Substitute any disturbance for El Niño, including those linked to human activity, and we have a way to think about other hybrids, like the coywolves or grolar bears or, in fact, ourselves. Some argue that Homo sapiens left Africa when its northern deserts were passable — that is, at a moment when the climate changed. We bumped into long-lost relatives in Eurasia, the equivalent of today’s polar bears in the grolar bears’ story, and mated.

We may, in turn, have adapted to Eurasian conditions by borrowing genes from these “locals.” Everyone except sub-Saharan Africans carry a small quantity of Neanderthal DNA that includes traits possibly important for survival in Eurasian environments — immune-system and skin-pigmentation genes, among others. And our current genome warehouses DNA from archaic humans that have otherwise disappeared. A recent study estimated that, in the same way that coywolves can be said to store wolf DNA that might have otherwise vanished from the Northeast, one-fifth of the Neanderthal genome endures, dispersed throughout humanity.

http://mobile.nytimes.com/2014/08/17/magazine/should-you-fear-the-pizzly-bear.html
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In the past, some researchers have tried to explain the demise of the Neanderthals by suggesting that the newcomers were superior to Neanderthals in key ways, including their ability to hunt, communicate, innovate and adapt to different environments.

But in an extensive review of recent Neanderthal research, CU-Boulder researcher Paola Villa and co-author Wil Roebroeks, an archaeologist at Leiden University in the Netherlands, make the case that the available evidence does not support the opinion that Neanderthals were less advanced than anatomically modern humans. Their paper was published today in the journal PLOS ONE.

“The evidence for cognitive inferiority is simply not there,” said Villa, a curator at the University of Colorado Museum of Natural History. “What we are saying is that the conventional view of Neanderthals is not true.”
Villa and Roebroeks scrutinized nearly a dozen common explanations for Neanderthal extinction that rely largely on the notion that the Neanderthals were inferior to anatomically modern humans. These include the hypotheses that Neanderthals did not use complex, symbolic communication; that they were less efficient hunters who had inferior weapons; and that they had a narrow diet that put them at a competitive disadvantage to anatomically modern humans, who ate a broad range of things.

The researchers found that none of the hypotheses were supported by the available research. For example, evidence from multiple archaeological sites in Europe suggests that Neanderthals hunted as a group, using the landscape to aid them.

Researchers have shown that Neanderthals likely herded hundreds of bison to their death by steering them into a sinkhole in southwestern France. At another site used by Neanderthals, this one in the Channel Islands, fossilized remains of 18 mammoths and five woolly rhinoceroses were discovered at the base of a deep ravine. These findings imply that Neanderthals could plan ahead, communicate as a group and make efficient use of their surroundings, the authors said.
Other archaeological evidence unearthed at Neanderthal sites provides reason to believe that Neanderthals did in fact have a diverse diet. Microfossils found in Neanderthal teeth and food remains left behind at cooking sites indicate that they may have eaten wild peas, acorns, pistachios, grass seeds, wild olives, pine nuts and date palms depending on what was locally available.

Additionally, researchers have found ochre, a kind of earth pigment, at sites inhabited by Neanderthals, which may have been used for body painting. Ornaments have also been collected at Neanderthal sites. Taken together, these findings suggest that Neanderthals had cultural rituals and symbolic communication.

Villa and Roebroeks say that the past misrepresentation of Neanderthals’ cognitive ability may be linked to the tendency of researchers to compare Neanderthals, who lived in the Middle Paleolithic, to modern humans living during the more recent Upper Paleolithic period, when leaps in technology were being made.
“Researchers were comparing Neanderthals not to their contemporaries on other continents but to their successors,” Villa said. “It would be like comparing the performance of Model T Fords, widely used in America and Europe in the early part of the last century, to the performance of a modern-day Ferrari and conclude that Henry Ford was cognitively inferior to Enzo Ferrari.”

Although many still search for a simple explanation and like to attribute the Neanderthal demise to a single factor, such as cognitive or technological inferiority, archaeology shows that there is no support for such interpretations, the authors said.

But if Neanderthals were not technologically and cognitively disadvantaged, why didn’t they survive?

The researchers argue that the real reason for Neanderthal extinction is likely complex, but they say some clues may be found in recent analyses of the Neanderthal genome over the last several years. These genomic studies suggest that anatomically modern humans and Neanderthals likely interbred and that the resulting male children may have had reduced fertility. Recent genomic studies also suggest that Neanderthals lived in small groups. All of these factors could have contributed to the decline of the Neanderthals, who were eventually swamped and assimilated by the increasing numbers of modern immigrants.

Neanderthals were not inferior to modern humans, study finds – ScienceDaily
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Tibetans live in a region that averages more than 4,000 meters above sea level. (Not for nothing is it called the roof of the world.) How did they come to be able to cope with their extreme environs? Some researchers in China and the United States think they might know, and their findings were published Wednesday in Nature. By sequencing DNA from a group of Tibetans and comparing the code to other gene databases, the researchers have discovered that Tibetans are inheritors of an ancient trait that helps regulate the oxygenation in their blood. But surprisingly, this trait did not arise in Homo sapiens. Rather, it came from another group of humans, the Denisovans—mysterious, little-known hominid cousins that died out some 40,000 years ago.

The new study on Tibetans demonstrates for the first time an evolutionary advantage conferred directly by Denisovans, an adaptation that seems to be singular to the Tibetan people. For people whose ancestors lived in milder altitudes, experiencing a dearth of oxygen at great heights causes the level of hemoglobin, the protein that carries oxygen in blood, to increase in attempt to compensate. But this raises the likelihood of cardiac events in the short term, and it is unhelpful for reproduction, as it increases the risk of preeclampsia (hypertension during pregnancy). Tibetans don’t have the same reaction to elevation: They have greater fitness and higher fertility even when there is little to breathe. This, along with other respiratory adaptations, allows them to thrive where others cannot.

Denisovans and Neanderthals are called extinct human “species”—a term that used to demark a clear line between two organisms incapable of interbreeding to produce fertile offspring. But the definition is no longer so clear. We know that these hominin cousins did couple with our Homo sapien ancestors—and some of us have inherited from them valuable modern traits. How we define “humans” past and present is a subject to contemplate—as fitting for scientists as for pilgrims to think about on their journeys across Tibetan plains.

Tibetans inherited Denisovan genetic adaptation for elevation: DNA for living at high altitude.
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ENIGMA MAN: A Stone Age Mystery

With Enigma Man we follow the groundbreaking research of Aussie paleoanthropologist Darren Curnoe and his Chinese colleague, paleontologist Ji Xueping.

Their study of ancient human remains found in a remote cave in South-west China looks at the idea there may have been another species of human existing alongside our ancestors as recently as 11,000 – 14,000 years ago.

Dubbed the ‘‘Red Deer Cave people’’, these ancient people, or, more precisely, their remains – so similar, yet so physically different from us – are much, much younger than our Neanderthal relatives, posing some seriously interesting questions. Were they really another human species? And if so, what happened to them? Why did they die out? How did they live? And what were their interactions with our own early relatives?

These are indeed big questions, Curnoe  says, and that’s what makes the search for answers so fascinating.

“The documentary is about the process of deciding: do we have a new species or not?” Curnoe, who is Associate Professor of evolutionary biology in the School of Biological, Earth and Environmental Sciences at UNSW, explains.

“The fossils just don’t fit with the dominant view in science at the moment about who was around 11,000 years ago or 14,000 years ago, how they relate to us, and how we think of ourselves as humans in relation to nature.

“We tend to think of ourselves as special. So it raises some pretty deep and challenging questions.

“There are views, which I subscribe to, and quite a lot of other people do too, that there are at least 30 different species that are in the fossil record that would be relatives of ours in some sense – some may be ancestors, some may be side-branches that went extinct.

“The classic example is the Neanderthals – everyone has heard of them, even if you don’t know much about them. What we are proposing is that instead of the Neanderthals being the last of the other human-like creatures [before it was] just us, we are in fact saying, well, no, this other group survived until much more recently.”

(Source: https://www.youtube.com/)
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In one new study of 1000 human genomes, Sriram Sankararaman and David Reich of Harvard Medical School and colleagues found that Neanderthal DNA is most common in regions of the genome with the greatest genetic variability, making them a prime target for natural selection. While Neanderthal DNA may make up only 1.6 to 1.8 per cent of the Eurasian genome, it punches above its weight in terms of biological impact, says Reich (Nature, DOI: 10.1038/nature12961).

Joshua Akey and Ben Vernot of the University of Washington in Seattle have analysed the Neanderthal DNA in a further 665 humans (Science, DOI: 10.1126/science.1245938). Both their study and the Harvard one found a hotspot of Neanderthal ancestry in genes relating to keratin, a fibrous protein found in our hair, skin and nails.

One of the genes, BNC2, is involved in skin pigmentation. That implies that Eurasians owe their paler skins partly to Neanderthals. Light skin is an advantage at higher latitudes because it is more efficient at generating vitamin D from sunlight, so Neanderthal DNA may have helped modern humans to adapt to life outside Africa.

If so, the adaptation took thousands of years to become universal. A third study published this week describes a DNA analysis of one person who lived in Stone Age Europe about 7000 years ago – 40,000 years after any Neanderthal interbreeding. His genes suggest his skin was dark (Nature, doi.org/q74). It may be that the Neanderthal keratin affected early Eurasians’ hair instead, perhaps straightening it.

…

Neanderthal DNA is irregularly spaced through the modern human genome rather than being fully mixed. That implies that interbreeding occurred very rarely. Sankararaman estimates it may have happened just four times.

http://www.newscientist.com/article/mg22129542.600-neanderthalhuman-sex-bred-light-skins-and-infertility.html
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